This invention relates, in general, to a method and apparatus for the deposition of metal nanoclusters and films on a substrate and more particularly, is directed to a deposition system incorporating a Jet Vapor Deposition (hereinafter, xe2x80x98JVDxe2x80x99) source apparatus utilizing a hydrogen atom (H atom) jet for the deposition metal nanoclusters and films.
Deposited thin films have major, diverse technological functions and enormous commercial value. There now exist diverse methods for vapor deposition of metals, semiconductors, insulators and organics, as well as complex multicomponents such as oxides and nitrides. In general, deposition methods fall into two classes. In Chemical Vapor Deposition (hereinafter, xe2x80x98CVDxe2x80x99), precursor molecules react at a heated substrate, usually at relatively high pressures, to generate species that comprise the deposited film. In Physical Vapor Deposition (hereinafter, xe2x80x98PVDxe2x80x99), the film species are generated some distance from the substrate, usually in a high vacuum; the gas phase mean free path is large, and film species travel by xe2x80x9cline of sightxe2x80x9d to deposit on the substrate.
Deposition techniques do not always fit this traditional description. The assignee of the present invention has developed a family of vapor deposition methods referred to as Jet Vapor Deposition (JVD), in which film species are made remotely, as in PVD, but the vacuum is xe2x80x9clowxe2x80x9d, and the mean free path is small. Film components travel xe2x80x9cline of sightxe2x80x9d because they are convected in a sonic, collimated, xe2x80x9cjet in low vacuumxe2x80x9d. Exemplary processes, based on patented JVD sonic nozzle sources such as the hot filament wirefeed, and the xe2x80x9celectron jetxe2x80x9d or xe2x80x9ce-jetxe2x80x9d, include deposition of metals such as Cu, Au, Ag, Sn, Pb, Ni, Ti, Ta, and many others, singly or as alloys, in simple or multilayer form. However, it is also possible in JVD to convect species to the substrate that then undergo film forming or film modifying reactions at the surface just as in CVD.
One area of particular interest regarding film deposition lies in emerging fuel cell technology where catalyst layers are provided to an ion exchange membrane in order to facilitate the electrochemical reaction needed to sustain electrical output. For efficient fuel cell operation, the catalyst layers must not only adequately contact the ion exchange membrane and adjacent anode or cathode electrodes, but also allow access to the gaseous reactants fed to each electrode, typically a hydrogen-rich gas and an oxygen-rich gas. The catalyst layers are typically deposited upon the ion exchange membranes through either a xe2x80x98wet chemistryxe2x80x99 process involving aqueous solutions at approximately atmospheric pressures, or by utilizing jet vapor technology, for example, sputtering or the like, operating at reduced pressures.
The wet chemistry process produces catalyst layer films of nanoclusters having the proper size and activity, but is not very efficient as many of the nanoclusters which contact the electrode material do not contact the ion exchange membrane while still other nanoclusters are lost deep in the pores of the membrane itself. Vapor deposition of catalyst layers is more efficient in depositing the nanoclusters at the electrode/membrane interface, however the activity of the resultant catalyst layer has yet to match the performance of the catalyst layers deposited as a result of the wet chemistry process. In essence, the wet chemistry process ensures appropriate catalysis, but is too inefficient while the vapor deposition improves efficiency, but suffers from poor catalytic activity. Moreover, the existing catalyst layer deposition processes are too uneconomical for large scale production.
The present invention therefore seeks to create a heretofore unknown hybrid process for the deposition of metallic nanoclusters, for use with technologies such as fuel cell applications, which is effective, economical and applicable to large scale production.
It is an object of the present invention to provide a method and apparatus for the deposition of metal nanoclusters and films on a substrate.
It is another object of the present invention to provide a method and apparatus for the deposition of metal nanoclusters and films on a substrate utilizing a hybrid JVD/wet chemistry process.
It is another object of the present invention to increase the efficiency of deposited film while reducing the cost to produce the same.
These and other objectives of the present invention, and their preferred embodiments, shall become clear by consideration of the specification, claims and drawings taken as a whole.